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3.
PROCEDURE UP TO DATA
COMMUNICATIONS DESCRIBED IN THIS GUIDEBOOK MELSEC
QnA
3.2.2
Self loopback test
The self loopback test checks the functions that communicate with the PC CPU and the CHI
(RS-232C) or CH2 (RS-422/485) interface send and receive functions.
a
Mode switches setting
Set the CHI and CH2 mode switches to "F" (self loopback test)
Transmission specifications switches setting
Set the CHI and CH2 transmission specifications switches as shown in Section 3.1.2.
Ish
Cable connection
Connect the CH1 (RS-232C) connector and CH2 (RS-422/485) terminal board with a
cable as shown below.
CH1 (RS-232C) Cable Connection
I
CH2 (RS-422/485) Cable Connection
I
1
AJ71QC24
I
I
I
I
AJ71 QC24
I
Cable
Connection
S i g n a l
Pin
No.
Cable
Connection
Signal
Name
Name
SDA
FG
1
SDB
I
1
~
SD
2
RD
3
4
~
RS
4
cs
5
4
DSR
6
SG
7
CD
8
DTR
20
-
~
-
~
I
I
I
I1
@
Connect the connector connecting the test cable shown above to the CHI RS-232C
connector.
@
At the CH2 RS-422/485, jumper the pins as shown above.
a
Self loopback test execution
@
Set the PC CPU RUN/STOP key switch to the STOP position.
@
When the PC CPU power is turned ON, or the CPU is reset, the QC24 Ready signal is
turned ON and the checks start automatically.
(The Ready signal is turned ON several seconds after the power is turned ON, or the
CPU is reset.)
@
Check sequence
Repeat the checks in (1) PC CPU communications check
+
(2) CHI RS-232C check
+
(3) CH2 RS-422/485 check order. (The QC24 does this automatically.)
@
Check the state of the LED displays shown on the next page
Normal
,.....,....
End the tet by performing item
@
below.
Error
,.............
Turn OFF the power, then check the modes switches, transmission speci-
fications switches, cable connections,etc. and set the switches correctly
and repeat the test.
3 - 6
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